The use of infrared radiation, sometimes called infrared light, in optical switching circuitry is well known. Typically, an infrared-emitting diode is employed to generate the infrared radiation which is directed through an optical path to an infrared detector, usually a solid state device such as a phototransistor or photothyristor, which functions as an "optical switch". When the optical path is blocked, the optical switch is turned off. For example, in a video-cassette recorder ("VCR") the technology is used to detect the beginning and ending of the video tape in the cassette. The tape in the cassette passes through the optical paths of the beginning-of-tape and end-of-tape detection devices. The magnetic coating on the tape blocks these optical paths; however, there are clear "leaders" at the beginning and ending of the tape which are transparent to infrared radiation. When these leaders pass through the beginning-of-tape or end-of-tape optical path, a signal is generated which triggers other VCR functions such as automatic on, off, or rewind.
The use of infrared optical switching in VCR's and other electrical/electronic equipment has created a need for a diagnostic instrument for testing the functioning of the infrared emitter(s) in the repair of these devices without requiring the removal of such emitter. Failures of the infrared emitter which is a part of the beginning-of-tape and end-of-tape detection circuitry in a VCR have been a source of frustration to VCR repair technicians in the past. When the emitter fails, the VCR simply will not operate at all when the power is turned on, a symptom of any of a number of possible problems. Accordingly, there is a real advantage in being able to quickly ascertain whether a failed emitter is the cause when this symptom is present. In the past, it has been necessary to remove the emitter from the circuit to test it, a process which takes approximately twenty minutes to complete and does not necessarily effect a repair of the VCR. Further, the voltage checks which have been commonly used in the past by technicians to test infrared emitters are not foolproof. This method sometimes indicates the emitter is good when, in fact, it has failed or is defective and will not emit infrared radiation as required.
Although various models of VCR's differ widely, the infrared emitter in the beginning-of-tape and end-of-tape circuitry is often located in a difficult to access position. An advantage of the present invention is that it may be inserted through the tape loading door or slot to test the emitter in a matter of seconds. Even if it were necessary to remove the case from the VCR to utilize the present invention, it would rarely add to the time necessary to effect repair of the VCR, as this is a step which is almost always performed by technicians when performing repairs.
Therefore, it is an object of the present invention to provide a VCR diagnostic instrument for checking the functioning of an infrared radiation emitter without removing such emitter from the VCR.
It is a further object of the present invention to provide a VCR diagnostic instrument which is dimensioned to be received within a VCR for testing the functioning of the infrared emitter with little or no disassembling of the VCR required.
It is also an object of the present invention to provide a method for testing the functioning of an infrared emitter which is more reliable than the method wherein electrical characteristics are checked at the terminals of such emitter.
It is another object of the present invention to provide a VCR diagnostic instrument for testing the functioning of an infrared radiation emitter which is self-contained and requires no external power source.
It is yet another object of the present invention to provide a VCR diagnostic instrument which is battery powered and includes a means for ascertaining battery condition.
It is another object of the present invention to provide a VCR diagnostic instrument which is simple and convenient to use.
It is a further object of the present invention to provide a VCR diagnostic instrument which is inexpensive to manufacture and maintain.
It is also an object of the present invention to provide a diagnostic instrument for checking the functioning of an infrared radiation emitter utilized in equipment other than VCR's.